Solid state lighting devices with dielectric insulation and methods of manufacturing

ABSTRACT

Solid state lighting devices and associated methods of manufacturing are disclosed herein. In one embodiment, a solid state lighting device includes a first semiconductor material, a second semiconductor material spaced apart from the first semiconductor material, and an active region between the first and second semiconductor materials. The solid state lighting device also includes an indentation extending from the second semiconductor material toward the active region and the first semiconductor material and an insulating material in the indentation of the solid state lighting structure.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.15/069,262, filed Mar. 14, 2016, which is a divisional of U.S. patentapplication Ser. No. 12/853,014, filed Aug. 9, 2010, now U.S. Pat. No.9,287,452.

TECHNICAL FIELD

The present technology is directed generally to solid state lighting(“SSL”) devices with dielectric insulation and associated methods ofmanufacturing.

BACKGROUND

SSL devices generally use semiconductor light emitting diodes (“LEDs”),organic light emitting diodes (“OLEDs”), laser diodes (“LDs”), and/orpolymer light emitting diodes (“PLEDs”) as sources of illuminationrather than electrical filaments, a plasma, or a gas. FIG. 1 is across-sectional diagram of a portion of a conventional indium galliumnitride (“InGaN”) LED 10. As shown in FIG. 1, the LED 10 includes asubstrate material 12 (e.g., silicon carbide, sapphire, or silicon), anN-type gallium nitride (“GaN”) material 14, an active region 16 (e.g.,GaN/InGaN multiple quantum wells (“MQWs”)), and a P-type GaN material 18on top of one another in series. The LED 10 can also include a firstcontact 11 on the P-type GaN material 18 and a second contact 15 on theN-type GaN material 14.

The GaN/InGaN materials 14, 16, and 18 of the LED 10 are generallyformed via epitaxial growth. The formed GaN/InGaN materials 14, 16, and18, however, typically include a high density of lattice dislocationsthat can negatively impact the optical and/or electrical performance ofthe LED 10. For example, as described in more detail later, the formedGaN/InGaN materials 14, 16, and 18 can include a plurality ofindentations that may form unintended carrier passages bypassing theactive region 16 during processing.

One conventional technique for addressing the high density of latticedislocations is to incorporate aluminum nitride (AlN), silicon nitride(SiN), and/or other suitable interlayers in the LED 10 (e.g., betweenthe substrate 12 and the N-type gallium nitride 14). The incorporationof such interlayers, however, cannot completely eliminate the latticedislocations in the GaN/InGaN materials 14, 16, and 18 of the LED 10.Also, incorporating interlayers adds cost and time to the manufacturingprocess of the LED 10. Accordingly, several improvements to at leastlessen the impact of the lattice dislocations in LEDs may be desirable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a portion of an LED in accordancewith the prior art.

FIG. 2A is a cross-sectional view of a portion of a microelectronicsubstrate undergoing a process for forming an SSL device in accordancewith embodiments of the technology.

FIG. 2B is a cross-sectional view of a portion of a microelectronicsubstrate undergoing a process for forming an SSL device in accordancewith conventional techniques.

FIGS. 2C-2F are cross-sectional views of a portion of a microelectronicsubstrate undergoing a process for forming an SSL device in accordancewith embodiments of the technology.

FIGS. 3A-3F are cross-sectional views of a portion of a microelectronicsubstrate undergoing another process for forming an SSL device inaccordance with additional embodiments of the technology.

DETAILED DESCRIPTION

Various embodiments of SSL devices with dielectric insulation andassociated methods of manufacturing are described below. The term“microelectronic substrate” is used throughout to include substratesupon which and/or in which SSL devices, microelectronic devices,micromechanical devices, data storage elements, read/write components,and other features are fabricated. The term “lattice dislocation”generally refers to a crystallographic defect or irregularity within acrystal structure. A lattice dislocation can include a V-defect, an edgedislocation, a threading (or screw) dislocation, and/or a combinationthereof. A person skilled in the relevant art will also understand thatthe technology may have additional embodiments, and that the technologymay be practiced without several of the details of the embodimentsdescribed below with reference to FIGS. 2A and 2C-3F.

FIGS. 2A and 2C-2F are cross-sectional views of a portion of amicroelectronic substrate 100 undergoing a process for forming an SSLdevice in accordance with embodiments of the technology. The SSL devicecan be an LED, an OLED, a LD, a PLED, and/or other suitable devices. Inthe following description, common acts and structures are identified bythe same reference numbers. Even though only particular processingoperations and associated structures are illustrated in FIGS. 2A and2C-2F, in certain embodiments, the process can also include forming alens, a mirror material, support structures, conductive interconnects,and/or other suitable mechanical/electrical components (not shown).

As shown in FIG. 2A, an initial operation of the process can includeforming an SSL structure 101 and an optional buffer material 103 on asubstrate material 102. The substrate material 102 can include a silicon(Si) wafer (e.g., with a Si(1,1,1) crystal orientation), aluminumgallium nitride (AlGaN), GaN, silicon carbide (SiC), sapphire (Al₂O₃), acombination of the foregoing materials, and/or other suitable substratematerials. In certain embodiments, the optional buffer material 103 caninclude AlN, GaN, zinc nitride (ZnN), and/or other suitable materials.In other embodiments, the optional buffer material 103 may be omitted,and the SSL structure 101 may be formed directly on the substratematerial 102.

The SSL structure 101 can include a first semiconductor material 104, anactive region 106, and a second semiconductor material 108 stacked oneon the other. In one embodiment, the first and second semiconductormaterials 104 and 108 include an N-type GaN material and a P-type GaNmaterial, respectively. In another embodiment, the first and secondsemiconductor materials 104 and 108 include a P-type GaN material and anN-type GaN material, respectively. In further embodiments, the first andsecond semiconductor materials 104 and 108 can individually include atleast one of gallium arsenide (GaAs), aluminum gallium arsenide(AlGaAs), gallium arsenide phosphide (GaAsP), gallium(III) phosphide(GaP), zinc selenide (ZnSe), boron nitride (BN), AlGaN, and/or othersuitable semiconductor materials.

The active region 106 can include a single quantum well (“SQW”), MQWs,and/or a bulk semiconductor material. As used hereinafter, a “bulksemiconductor material” generally refers to a single grain semiconductormaterial (e.g., InGaN) with a thickness greater than about 10 nanometersand up to about 500 nanometers. In certain embodiments, the activeregion 106 can include an InGaN SQW, InGaN/GaN MQWs, and/or an InGaNbulk material. In other embodiments, the active region 116 can includealuminum gallium indium phosphide (AlGaInP), aluminum gallium indiumnitride (AlGaInN), and/or other suitable materials or configurations.

The SSL structure 101 and the optional buffer material 103 can be formedon the substrate material 102 via MOCVD, molecular beam epitaxy (“MBE”),liquid phase epitaxy (“LPE”), hydride vapor phase epitaxy (“HVPE”),and/or other suitable epitaxial growth techniques. It has been observed,however, that the SSL structure 101 formed via the foregoing techniquestypically includes a high density of lattice dislocations. For example,as shown in FIG. 2A, the SSL structure 101 can include a plurality ofindentations 110 in the SSL structure 101. Three indentations 110 areshown in FIG. 2A for illustration purposes, and the dimensions of theindentations 110 are exaggerated for clarity.

As shown in FIG. 2A, the indentations 110 can include a plurality ofsidewalls 111 extending into the SSL structure 101. In the illustratedembodiment, the indentations 110 individually include sidewalls 111extending from a surface 108 a of the second semiconductor material 108into the active region 106 and the first semiconductor material 104. Inother embodiments, at least some of the indentations 110 can includesidewalls that extend only into the active region 106, or theindentations can extend into the optional buffer material 103 or eveninto the substrate material 102. In any of the foregoing embodiments,the SSL structure 101 can also include edge dislocations, threadingdislocations, and/or other lattice dislocations (not shown).

Without being bound by theory, it is believed that various structuraland/or operational conditions may cause the formation of theindentations 110 during processing. For example, it is believed thatindentations 110 may form due to different crystal growth rates alongdifferent crystal facets of the substrate material 102 (or the optionalbuffer material 103). It has been observed that epitaxial growth alongcertain crystal facets (e.g., c-plane) results in lower surface energythan other crystal facets (e.g., m-plane). As a result, epitaxial growthmay propagate along certain crystal facets faster than others to formthe indentations 110. It is also believed that contaminant particles onthe surface of the substrate material 102 and/or other epitaxial growthconditions may also cause the indentations 110 to form.

The indentations 110 can cause low optical efficiencies of the SSLstructure 101 when the microelectronic substrate 100 is processed inaccordance with conventional techniques. For example, as shown in FIG.2B, a conductive material 112 (e.g., silver) is formed on the secondsemiconductor material 108 as an electrical contact in accordance withconventional techniques. The conductive material 112 includes a firstportion 112 a on the surface 108 a of the second semiconductor material108 and a second portion 112 b in contact with the first semiconductormaterial 104. Thus, the second portion 112 b of the conductive material112 forms carrier passages 113 electrically connecting the first andsecond semiconductor materials 104 and 108. As a result, charge carriers(i.e., holes and electrons) from the first and second semiconductormaterials 104 and 108 may bypass the active region 106 and combinenon-radiatively in the carrier passages 113. Such non-radiativerecombination can thus cause low optical efficiencies in the SSLstructure 101.

Several embodiments of the process can at least reduce or eliminate therisk of forming bypassing carrier passages 113 by incorporating aninsulation material in the SSL structure 101. As shown in FIG. 2C,another operation of the process includes depositing an insulatingmaterial 118 on the SSL structure 101. The insulating material 118 caninclude a first insulating portion 118 a on the surface 108 a of thesecond semiconductor material 108 and a second insulating portion 118 bin the indentations 110. In the illustrated embodiment, the insulatingmaterial 118 generally conforms to the surface 108 a and the sidewalls111 of the indentations 110. In other embodiments, the insulatingmaterial 118 can partially or substantially fill the indentations 110,as described in more detail later with reference to FIG. 2F.

The insulating material 118 can include silicon dioxide (SiO₂), siliconnitride (SiN), hafnium silicate (HfSiO₄), zirconium silicate (ZrSiO₄),hafnium dioxide (HfO₂), zirconium dioxide (ZrO₂), aluminum oxide(Al₂O₃), and/or other suitable materials with a dielectric constanthigher than about 1.0 at 20° C. under 1 kHz. Techniques for forming theinsulating material 118 can include chemical vapor deposition (“CVD”),atomic layer deposition (“ALD”), spin-on coating, thermal oxidation,and/or other suitable techniques.

FIG. 2D shows another operation of the process, in which the firstinsulating portion 118 a (FIG. 2C) of the insulating material 118 isremoved from the SSL structure 101 while the second insulating portion118 b remains in the indentations 110. As a result, the insulatingmaterial 118 does not cover the surface 108 a of the secondsemiconductor material 108. In one embodiment, removal of the firstinsulating portion 118 a is stopped when the surface 108 a of the secondsemiconductor material 108 is exposed. In other embodiments, at least aportion of the second semiconductor material 108 may be removed beyondthe surface 108 a. Techniques for removing the first insulating portion118 a of the insulating material 118 include chemical-mechanicalpolishing (“CMP”), electro-chemical-mechanical polishing (“ECMP”), wetetching, drying etching, laser ablation, and/or other suitable materialremoval techniques.

FIG. 2E shows a subsequent operation of the process, in which aconductive material 120 is formed on the SSL structure 101 with theinsulating material 118. As shown in FIG. 2E, the conductive material120 includes a first conductive portion 120 a and a second conductiveportion 120 b. The first conductive portion 120 a is in contact with thesurface 108 a of the second semiconductor material 108 forming anelectrical contact for the SSL structure 101. The second conductiveportion 120 b is within the indentations 110 and in contact with thesecond insulating portion 118 b.

In certain embodiments, the conductive material 120 can include indiumtin oxide (“ITO”), aluminum zinc oxide (“AZO”), fluorine-doped tin oxide(“FTO”), and/or other suitable transparent conductive oxide (“TCOs”). Inother embodiments, the conductive material 120 can include copper (Cu),aluminum (Al), silver (Ag), gold (Au), platinum (Pt), and/or othersuitable metals. In further embodiments, the conductive material 120 caninclude a combination of TCOs and one or more metals. Techniques forforming the conductive material 120 can include MOCVD, MBT, spraypyrolysis, pulsed laser deposition, sputtering, electroplating, and/orother suitable deposition techniques.

The SSL device formed in accordance with several embodiments of theforegoing process can have improved optical efficiencies overconventional devices by eliminating bypassing carrier passages 113 (FIG.2B). For example, as shown in FIG. 2E, the second insulating portion 118b electrically insulates the second conductive portion 120 b from theactive region 106 and the first semiconductor material 104. The secondinsulating portion 118 b can thus prevent the second conductive portion120 b from forming carrier passages that would otherwise bypass theactive region 106 by directly connecting the first and secondsemiconductor materials 104 and 108. As a result, non-radiativerecombination of charge carriers (i.e., holes and electrons) inbypassing carrier passages can be at least reduced or generallyeliminated in the SSL structure 101.

Even though the insulating material 118 is shown as generally conformalto the SSL structure 101 in FIGS. 2C-2E, in certain embodiments, theinsulating material 118 can also have other configurations. For example,as shown in FIG. 2F, the second portion 118 b of the insulating material118 can substantially or completely fill the indentations 110, thesecond portion 118 b of the insulating material 118 can even extendbeyond the surface 108 a of the second semiconductor material 108.Subsequently, portions of the insulating material 118 that extend beyondthe surface 108 a may be removed via CMP, ECMP, and/or other suitabletechniques. Thus, the second insulating portion 118 b can be generallycoplanar with the surface 108 a of the second semiconductor material108. In other examples, the insulating material 118 can partially fillthe indentations 110 and/or have other suitable configurations. Infurther examples, the insulating material 118 may be formed beforeforming the second semiconductor material 108, as described in moredetail below with reference to FIGS. 3A-3E.

FIGS. 3A-3E are cross-sectional views of a portion of a microelectronicsubstrate 100 undergoing another process for forming an SSL device inaccordance with additional embodiments of the technology. As shown inFIG. 3A, an initial operation of the process can include forming a firstsemiconductor material 104 and an active region 106 on a substratematerial 102 (with an optional buffer material 103) via MOCVD, MBE, LPE,HYPE, and/or other suitable epitaxial growth techniques. The activeregion 106 has a surface 106 a facing away from the first semiconductormaterial 104.

As described above with reference to FIG. 2A, it is believed thatvarious structural and/or operational conditions may cause the formationof indentations 210 (three are shown for illustration purposes) duringepitaxial growth, as shown in FIG. 3A. In the illustrated embodiment,the indentations 210 have a plurality of sidewalls 211 extending fromthe surface 106 a of the active region 106 into the first semiconductormaterial 104. In other embodiments, at least some of the indentations210 can also have sidewalls extending into the optional buffer material103 and/or the substrate material 102.

As shown in FIG. 3B, another operation of the process includesdepositing the insulating material 118 on the microelectronic substrate100 such that the first insulating portion 118 a is on the surface 106 aof the active region 106 and the second insulating portion 118 b is inthe indentations 210. As shown in FIG. 3C, the process can furtherinclude removing the first insulating portion 118 a (FIG. 3B) of theinsulating material 118 from the microelectronic substrate 100 in afashion generally similar to that described above with reference to FIG.2D. The material removal operation may be stopped when the surface 106 aof the active region 106 is exposed while the second insulating portion118 b remains in the indentations 210.

As shown in FIG. 3D, a subsequent operation of the process includesforming the second semiconductor material 108 on the microelectronicsubstrate 100 via MOCVD, MBE, LPE, HVPE, and/or other suitable epitaxialgrowth techniques. The first semiconductor material 104, the activeregion 106, and the second semiconductor material 108 form a differentembodiment of the SSL structure 101. In one embodiment, the secondsemiconductor material 108 may grow into the indentations 210 via acombination of lateral and vertical growth. Thus, the secondsemiconductor material 108 includes a first semiconductor portion 108 aon the surface 106 a of the active region 106 and a second semiconductorportion 108 b in the indentations 210. In other embodiments, theindentations 210 may be filled with a filler material (e.g., AlN, notshown) before the second semiconductor material 108 is formed. Infurther embodiments, the second semiconductor material 108 may haveother suitable configurations. In any of the foregoing embodiments, thesecond insulating portion 118 b of the insulating material 118electrically insulates the second semiconductor material 108 from thefirst semiconductor material 104 and the active region 106.

In the illustrated embodiment, the second semiconductor material 108 hasa generally planar surface 108 a facing away from the active region 106.As shown in FIG. 3E, another operation of the process can includeforming a conductive material 120 on the generally planar surface 108 afor electrical connection to the second semiconductor material 108. Inother embodiments, the second semiconductor material 108 can also have anon-planar surface (not shown) and/or have other suitable structuralconfigurations.

FIG. 3F shows another embodiment of the process in which the secondinsulating portion 118 b of the insulating material 118 cansubstantially fill the indentations 210, which can be generally similarto the operation described above with reference to FIG. 2E. In theillustrated embodiment, the insulating material 118 is generallycoplanar with the surface 106 a of the active region 106. In otherembodiments, the insulating material 118 can be non-planar with thesurface 106 a and/or have other suitable configurations.

From the foregoing, it will be appreciated that specific embodiments ofthe technology have been described herein for purposes of illustration,but that various modifications may be made without deviating from thedisclosure. Many of the elements of one embodiment may be combined withother embodiments in addition to or in lieu of the elements of the otherembodiments. Accordingly, the disclosure is not limited except as by theappended claims.

I claim:
 1. A method for forming a solid state lighting device,comprising: providing a solid state lighting (SSL) structure on asubstrate material, the SSL structure including a first semiconductormaterial and an active region over the first semiconductor material;forming an indentation in the SSL structure, thereby exposing sidewallsof the first semiconductor material and the active region; depositing aninsulating material over the SSL structure, the insulating materialcovering exposed portions of the first semiconductor material and theactive region in the indentation; and depositing a second semiconductormaterial on the SSL structure over the indentation and a surface of theactive region, the second semiconductor material including (a) a firstportion in contact with the active region and (b) a second portion inthe indentation and separated from the first semiconductor material bythe insulating material.
 2. The method of claim 1 wherein theindentation is a V-shaped indentation.
 3. The method of claim 1 whereinthe sidewalls of the indentation converge toward one another as theyextend toward the first semiconductor material.
 4. The method of claim1, further comprising depositing a conductive material over the secondsemiconductor material.
 5. The method of claim 1 wherein depositing theinsulating material over the SSL structure includes depositing theinsulating material over an upper surface of the active region, themethod further comprising: prior to depositing the second semiconductormaterial, removing the insulative material over the upper surface of theactive region, the insulating material in the indentation remaining. 6.The method of claim 5, wherein depositing the insulating materialincludes depositing the insulating material prior to forming aconductive material over the second semiconductor material.
 7. Themethod of claim 6, further comprising depositing a conductive materialover both the second semiconductor material and the insulating materialin the indentation.
 8. The method of claim 5, wherein the insulatingmaterial remaining in the indentation generally fills the indentation.9. The method of claim 1, wherein depositing the insulating materialincludes depositing the insulating material in the indentation andgenerally conforming to the sidewalls of the indentation.
 10. The methodof claim 1, wherein depositing the insulating material over the SSLstructure includes at least partially filling the indentation with theinsulating material.